1. Field of the Invention
The present invention generally relates to a socket, a circuit board, and a sub-circuit board for a semiconductor integrated circuit device, and more particularly to structures and methods for connection and disconnection of the socket, the sub-circuit board, and the circuit board.
2. Description of the Related Arts
Semiconductor integrated circuit (IC) devices are tested by various methods in order to verify their reliability. These tests include an electrical characteristics test and a burn-in test. The electrical characteristics test determines whether the characteristics of a semiconductor IC fall within the specifications of the IC, and the burn-in test applies temperature, voltage, and/or operating signals that are beyond the normal operating levels, to a semiconductor IC to detect latent defects which might appear at an early stage of regular use of the IC.
Generally, in testing, a semiconductor IC is placed in a socket that is fixed on a test circuit board that transfers electrical signals between the semiconductor IC and a tester. FIG. 1 through FIG. 3 are cross-sectional views showing three conventional methods for connecting a semiconductor IC 20 to a socket 70 and a test circuit board 80.
FIG. 1 shows a method for electrically connecting socket 70 and test circuit board 80. This method is mainly employed in Burn-In Test. For connection between socket 70 and test circuit board 80, connection leads 75 of socket 70 are inserted into through-holes 82 of test circuit board 80, and fixed by a soldering.
The connection method of FIG. 1 has a number of drawbacks. In particular, due to the use of solder 66, the connection method of FIG. 1 may cause lead poisoning of worker. In addition, when either socket 70 or test circuit board 80 is defective, separating socket 70 from test circuit board 80 for replacement of the defective component is difficult. In particular, the separation process includes heating test circuit board 80 to melt solder 66, and the heating may damage the wiring patterns (not shown) of test circuit board 80. Further, extended use of socket 70 and test circuit board 80 degrades the integrity of the bond created by solder 66, and the connection between socket 70 and test circuit board 80 becomes weak. This weakened connection can cause invalid test results.
The connection method of FIG. 2 between socket 70 and a test circuit board 100 is mainly employed in test handlers for electrical characteristics test. In this method, a receptacle 87 serves as an intermediate connection medium between socket 70 and test circuit board 100. Receptacle 87 is inserted into through hole 102 in test circuit board 100 and fixed by soldering. Then, connection leads 75 of socket 70 are inserted into respective receptacles 87. Separation of socket 70 from test circuit board is relatively easy because connection leads 75 make only temporary contacts with receptacles 87. However, the method in FIG. 2 has a number of disadvantages. First, to insert connection leads 75 into receptacles 85, external forces must be applied. Second, when connection leads 75 are fine-pitched, the method in FIG. 2 has a higher probability of short circuits and/or current leakage between neighboring through holes 102 than the method in FIG. 1 because the diameter of the through holes 102 is greater than that of through holes 82. In particular, each hole 102 must be wide enough to contain a receptacle 87, and thereby the distance between neighboring through holes 102 is relatively small. Third, adding and installing receptacles 87 increase the cost of IC tests.
To avoid the short circuits between neighboring through holes 102 in FIG. 2, a sub-circuit board 90 can be interposed between a socket 50 and test circuit board 100, as shown in FIG. 3. Sub-circuit board 90 has socket 50 thereon, and wiring patterns in sub-circuit board 90 electrically connect the connection leads (not shown) of socket 50 to respective through holes 92 of sub-circuit board 90. Connection pins 95 and receptacles 87 are respectively fixed to through holes 92 and through holes 102 by soldering. Then, connection pins 95 of sub-circuit board 90 are inserted into respective receptacles 87. However, even though sub-circuit board 90 can reduce or eliminate the short circuit problem, the connection method still has high test cost due to the additional components such as receptacles 87.
An embodiment of the present invention provides a socket and a circuit board, with or without a sub-circuit board for semiconductor integrated circuit device. The structure of each component in this invention provides convenient connection and disconnection of the socket or the sub-circuit board to and from the circuit board and low test cost by eliminating the use of solder and receptacles in the circuit board.
In accordance with an aspect of the present invention, the socket has distinctively shaped socket leads that are easily inserted into the through holes of circuit board. In addition, shape-induced elasticity of the socket leads provides a solid contact between the socket leads and the inner wall of the through holes.
The circuit board includes through holes where the socket leads are inserted, and the inner wall of the through holes are plated with conductive abrasion-resistant materials. Respective through holes are connected to a tester by wirings of the circuit board.
The sub-circuit board provides a connection between a socket, especially for fine-pitch semiconductor IC packages, and a circuit board. The sub-circuit board comprises through holes, wiring patterns which electrically connect the socket to the through holes, and connection leads. An end of each connection lead is fixed to the through holes, and the other end of the connection lead has a distinctive shape in the same manner as in the socket leads according to the present invention.
Moreover, the elasticity given to the socket leads and the connection leads of sub-circuit board extends the life of the socket and the sub-circuit board, since the socket leads and the connection pins recover their shape as soon as they are pulled out from the through holes of the circuit board.